Rock drill



March 5, 1935; r J. c. cuRTlsi 1,993,501

nocx DRILL Filed April 1, i951 Z6 27 1; 24am I Fg H 4 JoH/v newer/5 INVENTOR ATTORNEY v Patented Mar. 5, 1935 UNITED STATES PATENT OFFICE ,Cleveland Rock Drill Company,

Cleveland,

Ohio, a corporation of Ohio v V Application April 1, 1931, Serial No. 526,901

r 3 Claims.

This invention relates broadly ,to fluid actuated tools and moreparticularly to improvements in valvular mechanism therefor.

One of the objectsof this invention is to provide an arrangement of passage-ways within a fluid actuated machine which will facilitate the automatic movement of the valve element dis.-,

posed within said passage-ways and subject to the influence of the motive fluid.

' Another object of this invention is to construct a valve of relative light weight thus readily responsible to the effort of motive fluid.

Another object of this invention is to provide a fluid actuated machine with a valve having a relatively small displacement but capable to admit a sufficient amount of motive fluid to the working element of the mechanism.

Another object of this invention is to provide a fluid actuated machine with a piston chamber formed with extensive compression chamber in registration with a valve adapted to efliciently regulate the flow -of motive fluid thereto, thus reducing the air consumption as well as the cost of operation of the machine.

foregoing and the manner in which all the various objects are realized, will appear in the fol-, lowing description, which considered in connection with the accompanying drawing, sets forth the preferred embodiment of the invention.

In the drawing:

Figure 1 is a longitudinal sectional view of a:

fluid actuated tool illustrating the improved valvular element with the hammer at the beginning'of the its forward stroke.

Figure 2 is a view similar to Figure 1 illustrating the hammer at the beginning of its rearward stroke.

Figure 3 is a crosssectional view of the same taken on a plane indicated by the line 33 in Figure 1.

Figure 4 is-a view similar to Figure 3 taken on a plane indicated by the line 4-4 on Figure 1. The embodiment herein chosen to illustrate theinvention is a paving breaker of the hammer type which comprises a cylinder 10 within which there is reciprocablymounted a piston 11 having Other objects more or less ancillary to the:

formed with an aperture 19 and having at one end an annular ledge or valve seat 20.

I Secured to the cylinder by a pair of bolts (not shown) there is a backhead 21 providedwith a throttle valve 22 having an orifice 23 adapted 5 for registration with the chamber 24 through passage 25. In fluid tight engagement with the backhead 21 and the outer end of the cylinder 10, there is a valve block 26 formed with internally disposed differential cylindrical chambers 2'7 and 28 constituting at their intersection an annular shoulder 29 machined to produce a protuberant ledge or valve seat 30 similar to the valve seat 20. I

Intermediate the valve seats and 30, there is a disc valve 31, formed with two parallel faces 32 and, 33 and having its circumferential wall engaging the internal Wall of the cylindrical chamber 28. The valve 31 is provided with a hollowstem 34 slidably engaging the wall of the cylindrical chamber 27 and having its wall formed with a plurality of restricted passages 35. The thickness of the disc 31 is'coordinated with the vertical distance between the two valve seats 20 and 30 to permit a reciprocative movement of the valve and the alternative admission of compressedfluid into either the front end of the cylinder through a plurality of passages 35, 36, and 37 or to the rear end ofthe cylinder through enlarged passage 19.

Within the wall of the cylinder 10, there is disposed several chambers 38 and 39 in constant registration with the front and rear piston chambers 40 and 41'through radially disposed restricted ports 42 and 43, the purpose of which will be explained later.

An orifice or exhaust port 44 in the cylinder 10 is arranged in relation to the extremetravel of the piston to afford fluid communication -be-' tween the piston chambers 40 and 41 and the atmosphere. I

In the operation of the device, assuming the parts to be positioned asillustrated in Figure 1, motive fluid is admitted in the chamber 24 through the throttle valve opening 23 and passage to flow in the valve chamber 27 through port 45, and circumventing the valve 31 will flow to the rear end of the cylinder through aperture 19 and by expansion will drive the piston forwardly upon the buffer block 15 to deliver its blow to the cutting tool. The motive fluid being directly admitted upon the rear piston face 12 will urge the piston'forwardly previous to the admission of the motive fluid within the chamhers 38 through the restricted ports 42, thus preventing an excessive drop of pressure within the cylinder chamber 40 prior to the forward displacement of the piston.

After the piston has covered the exhaust port 44, the motive fluid remaining within the front end of the cylinder would be greatly compressed by the piston during its forward displacement due to the remote position of the exhaust port 44 in relation with the buffer block 15, and consequently would create a pressure which would have the tendency to retard or prevent a complete forward stroke of the piston, thus reducing the force of impact upon the cutting tool or buffer block 15. With the present design the compression chambers 89 afford a greater vol-..

ume, thus reducing to a minimum the pressure resulting from the compression without increasing the length of the machine. It is, obvious that if the compression chambers 39, in communication with the front piston chamber 41-, were not located within the wall of the cylinder, the chamber 41, i. e. the chamber circumventing the buffer block 15, would have to be greatly increased to provide a sufficient volume and prevent a high compression of the fluid during the forward movement of the piston. It would consequently result in increasing the length of the machine as well as its weight, andalso would require a longer buffer block 15 protruding from its casing 14. It has been found in practice that the use of a buffer block protruding f'rom its casing a distance greater than its diameter is impractical, the powerful impact of the piston upon that extended unsupported portion of the block causes the breakage thereof and consequently increases the cost of operation. The compression chambers 39 are calculated in such a way as to permit a suflicient pressure to take place within the piston chamber 41 during the forward movement. of the piston. That pres ure is conveyed into the valve block chamber 27 through the passages 37 and 36 to act upon the valve stem 34 tending to throw the valve forwardly. After the exhaust port 44 is uncovered by the rear piston face 12, a portion of the mo tive fluid will flow from the rear piston chamber 40 to atmosphere, thus reducing the pressure upon the valve face 32. The fluid compressed by the piston acting on the valve stem 34 will overcome the reduced pressure upon the valve face 32 and throw. the valve forwardly or in the position illustrated in Fig. 2.

After the piston has struck the buffer block 15 and with the valve in the position illustrated in Fig. 2, motive fluid flows from the chamber 28, through the plurality of valve restricted orifices 35 into the chamber 27, thus exerting pressure upon the stem 34 to maintain the valve in its lower position. From the chamber 27, motive fluid is admitted to the front end of the cylinder through passages 36 and 37 to act upon the front piston face 13., to drive the piston rearwardly.

During the rearward movement of the piston and after the exhaust port 44 is covered thereby, the motive fluid remaining within the rear piston chamber 40 being compressed by the piston would obviously retard and shorten the stroke thereof. However with the compression chambers 38 in constant communication with that portion of the cylinder through the restricted ports 42, the volume of the piston chamber is made greater without increasing the length and the weight of the machine, and consequently prevents an objectional high come pression within that portion of the cylinder, thus permitting a quick and complete return of the piston with a limited amount of motive fluid acting upon its front face 13, and permitting a suflicient pressure to act upon the exposed area of the valve face 32 tending to throw the valve rearwardly.

After the exhaust port 44 is uncovered by the piston, a portion of the motive fluid within the front piston chamber 41 will flow to atmosphere through the exhaust port 44, reducing thereby thepressure upon the valve stem 34 and allowing the valve to be shifted rearwardly by the compression exerted upon the exposed portion of the valveface 32 Motive fluid is then again admitted to the rear piston chamber 40 and by expansion will" drive the piston forwardly upon the buffer block-15 to deliver its blow to the cutting tool. The ports 42 connecting the compression' chambers 38 with the piston chamber 40 are restricted to, restrain, the admission of motive fluid within said chambers before the piston 11 is moved forwardly, consequently the motive fluid by expansion, will first act upon the piston before, it. is expanded within the charm. bers 38 thus preventing an excessive drop of pressure in the, piston, chamber 40 prior to, the forward movement of the piston.

Although the foregoing description is necessarily of a detailed character, in order tocompletely set forth, the invention, it isv to be understood that the'specific terminology is. not. in-

tended, to be, restrictive or confining and it is, to

be furtherunderstood that, various rearrangements of parts and modification of structural detail may be resorted to, withoutdeparting from the scope or spirit of the invention as herein claimed.

I claim:

1. In a rock drill, a cylinder having a piston reciprocable therein, a, valve block formed with a valve chamber, a valve reciprocably mounted within said chamber, said valve comprising a disk and a stem both capable of slidable engage ment with the internal wall of said chamber, means, for constantly admitting motive fluid into said chamber on each side of said disk, an inlet passage controlled by said disk for admitting motive fluid from said chamber into the rear end of said cylinder, ports caried by said stem for supplying motive fluid from said chamber to passages leading into the front end of said cylinder, actuating areas for said valve alternatively subjected to compressed fluid from said cylinder and means for actuating said valve including saidinlet passage for admitting compressed fluid from said cylinder to one of said areas and said passages for simultaneously exhausting compressed fluid previously admitted from said cylinder to the other of said areas.

2. In a rock drill, a cylinder having a piston reciprocable therein, a valve block formed with a valve chamber, a valve reciprocably mounted within said chamber, said valve comprising a stem and a disk both guided against lateral movement by their respective slidable engagement with the inner wall of said chamber, means independent of said valve for constantly admitting motive fluid on both sides of said disk, an inlet passage controlled by said disk for admitting motive fluid from said chamber? into the rearend of said cylinder, ports caried by said stem for supplying motive fluid from said chamher to passages leading into the front end of said cylinder, an actuating area on each side of said disk alternatively subjected to compressed fluid from said cylinder and means for actuating saidvalve including said inlet passage for admitting compressed fluid from said cylinder to one of said areas and said passages for simultaneously exhausting compressed fluid previously admitted from said cylinder to the other of said areas.

3. In a rock drill, a cylinder having a piston reciprocable therein, a valve block formed with a valve chamber, a valve reciprocably mounted Within said chamber, said valve comprising a stemand a disk both guided against lateral movement by their slidable engagement with the inner Wall of said chamber, common means for constantly admitting pressure fluid on each side of said disk over the marginal edge thereof,

opposed annular valve seats within said valve block with which each side of said disk is capable of alternative engagement for controlling the admission of the pressure fluid into the ends of said cylinder, an actuating area on one side of said disk equal to the inner area of its corresponding annular valve seat subjected to the action of the compressed fluid from said cylinder for actuating said valve away from said valve seat, and an opposed actuating area on the other side of said disk equal to the inner area of its corresponding annular valve seat subjected to the compressed fluid from ,said cylinder for actuating said disk away from said last mentioned valve seat.

JOHN C. CURTIS. 

